The present invention relates in general to solvents, and in particular to a new and useful solvent which can be used in the making of foamed plastic, in particular, PVC foam.
A wide variety of foamed plastics are known which can be manufactured according to many conventional techniques.
Foamed plastics range in density anywhere from one tenth to sixty pounds per cubic foot, and range from a rigid material suitable for structural use, to flexible cushion like substances. The foamed plastic may also have a wide range of cellular formations from open cells, to interconnected cells, to closed cells. For the making of PVC foam having a closed or substantially closed construction, a set of solvents are added to PVC pellets in steps. The solvents which are commonly referred to as carrying agents, include methylene chloride, trichloroethylene, fluorinated hydrocarbon (HCFC or CFC) FREON (a trademark identifying a group halogenated hydrocarbons containing one ore more fluorine atoms), ethyl acetate and toluene.
It is common practice to vary the proportions of the foregoing solvent components, and even to eliminate one or more component by increasing another component.
A blowing agent is also added which, when heated, produces gas which forms the cells of the product. Examples of suitable blowing agents for PVC foam products are sodium bicarbonate, halocarbons such as CC13 F, and hydrazine.
To form the foamed product, the mixture is supplied to a heated mold where it expands to fill the space of the mold.
Several if not all of the solvent or carrying agent components of known PVC foaming processes are environmentally undesirable.
The chlorinated and fluorinated components are particularly damaging to the environment and are being subjected to ever increasing Government regulation. The aromatic components such as toluene are also undesirable and pose safety hazards to the workers involved in making the foam products.
Accordingly an alternate solvent or carrying agent which avoids some or all of the objectionable carrying components would be particularly useful.